Study On Hydrodynamic And Mass Transfer Performance Of Metal Sheet Structured Packings In A CO₂Absorption Tower

CO2capture and storage (CCS) is the main solution of tackling climate change. It is very important for reducing energy consumption and cost of CO2absorption process to developing low pressure drop, high capacity and high efficient packings. Compared with random packings, structured packings are suitable for CO2capture process because of high void fraction and big mass transfer area.This paper studies the hydrodynamic and mass transfer performance of16kinds of metal sheet structured packings with different geometry parameters in a process of trace CO2absorption in the air with aqueous NaOH solution. Hydrodynamic study shows that the three geometry parameters of metal sheet structured packings (corrugated angle a, addendum angle β, corrugated peak height h) have a big impact on pressure drop. When a and β are small, the packings exhibit big pressure drop. When h is low, the pressure drop of packing is small. Several conclusions are obtained by studying the mass transfer performance of the packings above. With the improvement of gas/liquid flow rates the effective mass transfer area increases gradually. When gas/liquid flow rates reach a certain degree, the effective mass transfer area may surpass the specific area of the packings; When h=9mm, under low gas flow rate packings with a of30°and β of75°exhibit the best mass transfer efficiency. However under high gas flow rate packings with a of60°and β of75°perform best; When h=12mm, packings with a of30°and β of105°erform best in mass transfer under different gas/liquid flow rates; Liquid flow rate has a small impact on liquid phase mass transfer coefficient. With the improvement of gas flow rate and concentrations of NaOH aqueous solutions, the liquid phase mass transfer coefficient increases greatly; Chemical enhancement factors do not change with liquid flow rate. But with the increasement of gas flow rate chemical enhancement factors move downwards greatly; Chemical enhancement factors increase significantly with the improvement of concentrations of NaOH aqueous solution. But when the concentration surpass0.2mol/L chemical enhancement factors reach the maximum value of10and do not change with concentration again.In this paper, Mellpak250Y is compared with packings (a=60°, β=75°, h=9mm) designed by this experiment in terms of the effective mass transfer area. The former is lower than the latter by average19%. Thus the packing designed by this experiment is better than the commercial packing.Considering the effect of gas/liquid flow rates in this paper a new mathematical model is proposed to calculate the effective mass transfer area and liquid phase mass transfer coefficient and fits the experiment results with a good agreement. It indicates that this model can predict the mass transfer performance of the packings. Leva and Bain-Hougen correlations are used to calculate pressure drop and gas velocity of flooding respectively. The average relative deviation between calculated value and experimental value is within14.1%.This demonstrates that the models above can predict the hydrodynamic performance of packings.